Polyimide (PI), and in particular polyetherimide (PEI), are high-temperature engineering thermoplastic polymers with outstanding mechanical properties, thermal stability, and chemical resistance. Due to these excellent properties, PI, and in particular PEI, are widely used as matrix polymers, adhesives, and coatings in fields such as aerospace and advanced microelectronics. PEI polymers derived from 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl] propane dianhydride (BPADA) (such as the PEI polymer that is commercially available under the trade name ULTEM from SABIC) can be melt processed at 340° C. due to the flexible linkages in the PEI polymer backbone, for example, ether (—O—) and isopropylidene [—C(CH3)2—]. The viscosity of the high molecular weight polymers gives high viscosity which can lead to slower cycle time while injection molding or require higher temperatures than desired for the molding process. These drawbacks can be observed particularly in high molecular weight PI and PEI polymers.
Accordingly, there remains a need in the art for PI and PEI polymers that possess lower viscosity at processing temperatures and/or can be processed at lower temperatures. It would also be useful if the PI and PEI polymers could be processed by methods other than melt extrusion, for example methods such as solution-casting.